Move Code of Conduct out of Google Docs and into its own page

[krusynth]

I know it's easier to maintain a read-only version on Google but it makes more sense to keep this here with the other stuff imho where it's easily accessible. Open to debate.

[bensheldon]

As discussed on Discord: yep, let's do this 👍🏻

We expect that there will be revisions once there is a rules committee in place; that shouldn't stop this work now.